Conventionally air seeders separate or meter the particulate materials including seeds and fertilizer into distribution ducts through which the to materials are carried by an air stream generated by a fan and supplied to the ducts. The metering is effected by providing a series of distribution heads so that the material is initially metered into a pipe and then the distribution heads split the pipe firstly into a first series and then each of the first series is split into a second series. In this distribution head system, blockages are usually monitored by a monitor system which provides a sensor in each duct which is used to detect when the passage of seeds is halted due to a blockage.
An alternative technique for metering the material involves the use of a commercially available system manufactured by Valmar Airflow Inc. which individually meters from a supply tank into a plurality of cups with each cup supplying the metered material into a venturi. In this system, the metering arrangement and tank for a first particulate material such as seeds is arranged on one side of the machine and the metering system for the other materials such as fertilizer is arranged side by side with the first. The metering systems face toward the tractor operator pulling the machine so that the operator can visually see the feeding of the material into the cups and can thus make note of any blockages which occur.
These arrangements have a number of disadvantages and it is one object of the present Invention to provide an improved machine of this general type.